Reasons 7 - 9.
7. Luke 1:1-4
Luke gives his purposes for writing, and his purposes give credibility.
Don’t impose modern standard of history writing
8. Hard Sayings of Jesus
Luke 14:26 (Matthew 10:37)
9. What doesn’t appear in the gospels that you would expect?
Speaking in Tongues
Errors of the blog world: why only one non-Christian historian wrote about Jesus?